1. Field of the Invention
The present invention relates generally to impervious dehydrating containers that include reclosable caps.
2. Description of Related Art
Humidity-sensitive products that should be packaged in a controlled-atmosphere environmental medium include, in particular, products that desirably need to be protected so that their efficacy does not change due to a reaction with the humidity present in the ambient gaseous atmosphere and/or so that their physical integrity is preserved over time. In addition, it is often desirable to protect such products in order to avoid a change in their mechanical cohesion or their chemical behavior.
Packaging developed for such products usually comprises dehydrating materials such as, for example, silica gel and/or molecular sieves, which have the ability to act as a dehydrator of ambient gases inside the casing. Such casings are typically designed to be as impervious as possible.
A practice described in WO 03015060 involves verifying the humidity content inside a package by means of an indicator in direct contact with the ambient atmosphere of the package. The assembly includes an indicator tag formed by a soluble ink that is capable of migrating based on changes in the humidity content on a porous medium. The indicator tag can be seen through an opening present in the package, but is protected from the external atmosphere by a transparent protective layer impermeable to steam. An observer can thus visually see the migration of the ink and therefore determine if the packaged product has deteriorated. Such a design is complex because it requires the juxtaposition of a plurality of layers of which some, transparent and impermeable. This is difficult to implement in the case of containers produced at high speed by injection molding techniques from so-called convenience thermoplastic materials, which are often used to reduce the costs. In addition, as some products are sensitive to light, the inclusion of a viewing window can be unsuitable in some cases.
U.S. Pat. No. 4,990,284 describes a similar practice concerning the verification of the humidity content of a product packaged in a steam-proof impermeable transparent external casing, comprising, on the internal surface an indicator in the form of an impression produced with an ink having the ability to change color depending on the ambient humidity. It is necessary to remember that any casing, for example an overwrapping such as a film coated with strong barrier materials, allows humidity to pass over the long term, in particular through seams. The overwrapping overlapping the first primary packaging in contact with the product to be protected is permanently broken at the time of the first opening. Therefore, this approach is not suitable for the aforementioned need to view a humidity state of an enclosed gaseous medium, during recurrent uses, but is to be considered to be an indicator of the state at the first opening only.
Another practice described in document WO 0109601 consists of knowing the hygrometric state of a dehydrating material acting as a humidity sensor inside a package. A silica gel or an amorphous silica acting as the dehydrating material is impregnated with a copper salt-based ionic composition having the ability to change color according to the humidity state around the ionic composition.
Furthermore, this same document describes a paper or non-woven tag that constitutes a medium impregnated or coated with an ionic solution containing a copper salt capable of changing color according to the ambient humidity content. Ionic solutions can have different concentrations in order to control the changes in hue. Such materials, paper and woven or non-woven textiles generally make it possible to package granular dehydrating materials. This approach by impregnation of a support is suitable for observing the change in the dehydrating agent thus packaged.
U.S. Pat. No. 5,293,996 describes a package for integrated circuits containing a humidity indicator of which the color changes according to the hygrometric change, visible from the outside by a window incorporated in the package. The humidity indicator is positioned inside the package to the right of this window. The container is divided into three sections and one of these sections contains a compartment housing the humidity indicator. The humidity indicator is preferably a card. The card is simply placed in the compartment, thus making it visible from the outside. The composition of the packaging material of the compartment containing the humidity indicator card is a transparent plastic that enables the humidity indicator card to be viewed from the outside of the container.
U.S. Pat. No. 6,827,218 also describes a container for humidity-sensitive electronic equipment, such as, for example, an integrated circuit, including a tray, in which the integrated circuit is located, a cover that is attached to the tray, said cover being made of at least one dehydrating thermoplastic composition consisting of a polymer material, a dehydrating material and, in addition, an electrostatic charge dissipating material. The tray and cover constitute a primary package. This cover comprises an opening closed by an additional transparent part, to which the humidity indicator is attached on the internal side.
The primary package equipped with its indicator is placed in a secondary, flexible, transparent, barrier package, protecting the primary package, and in particular the dehydrating cover of which the main function is to dehydrate both the contents of the primary package as well as the gaseous volume located between the primary package and the secondary protective overwrapping. Therefore, the primary container is not impervious to humidity, and its dehydrating cover is there to keep the humidity level of said container as low as possible.
Moreover, such packages are difficult to implement, and while they may be suitable for integrated circuit-type products, with additional functionalities such as electrostatic discharge, they are not suitable for convenience products packaged in disposable packages and therefore that must be produced in large numbers and at the lowest costs.